The Dual Role of IL-2 in the Generation and Maintenance of CD8 + Memory T Cells Zhenhua Dai, Bogumila T. Konieczny and Fadi G. Lakkis This information is current as J Immunol 2000; 165:3031-3036; ; of September 30, 2021. doi: 10.4049/jimmunol.165.6.3031 http://www.jimmunol.org/content/165/6/3031 Downloaded from References This article cites 31 articles, 17 of which you can access for free at: http://www.jimmunol.org/content/165/6/3031.full#ref-list-1 Why The JI? Submit online. http://www.jimmunol.org/ • Rapid Reviews! 30 days* from submission to initial decision • No Triage! Every submission reviewed by practicing scientists • Fast Publication! 4 weeks from acceptance to publication *average by guest on September 30, 2021 Subscription Information about subscribing to The Journal of Immunology is online at: http://jimmunol.org/subscription Permissions Submit copyright permission requests at: http://www.aai.org/About/Publications/JI/copyright.html Email Alerts Receive free email-alerts when new articles cite this article. Sign up at: http://jimmunol.org/alerts The Journal of Immunology is published twice each month by The American Association of Immunologists, Inc., 1451 Rockville Pike, Suite 650, Rockville, MD 20852 Copyright © 2000 by The American Association of Immunologists All rights reserved. Print ISSN: 0022-1767 Online ISSN: 1550-6606. The Dual Role of IL-2 in the Generation and Maintenance of CD8؉ Memory T Cells1 Zhenhua Dai, Bogumila T. Konieczny, and Fadi G. Lakkis2 The mechanisms responsible for the generation and maintenance of T cell memory are unclear. In this study, we tested the role of IL-2 in allospecific CD8؉ T cell memory by analyzing the long-term survival, phenotype, and functional characteristics of IL-2-replete (IL-2؉/؉) and IL-2-deficient (IL-2؊/؊) CD8؉ TCR-transgenic lymphocytes in an adoptive transfer model. We found that IL-2 is not essential for the in vivo generation, maintenance, or recall response of CD8؉ memory T cells. However, IL-2 increased the size of the CD8؉ memory pool if present at the time of initial T cell activation but reduced the size of the pool if present during memory maintenance by inhibiting the proliferation of CD8؉ memory T cells. Thus, IL-2-based vaccine strategies or immunosuppressive regimens that target IL-2 should take into account the divergent roles of IL-2 in CD8؉ T cell immunity. The Journal of Immunology, 2000, 165: 3031–3036. Downloaded from defining feature of the adaptive immune response is its In this study, we tested whether IL-2 is required for generating ability to generate memory lymphocytes (1–3). Upon and maintaining CD8ϩ memory T cells by analyzing the long-term encounter with a foreign Ag, Ag-specific T lymphocytes survival, phenotype, and functional characteristics of Ag-activated A ϩ/ϩ Ϫ/Ϫ proliferate and differentiate into effector cells. The majority of ef- IL-2-replete (IL-2 ) (3) and IL-2 gene-knockout (IL-2 ) fector cells undergo apoptosis after the Ag is eliminated (4). The CD8ϩ TCR-transgenic (TCR-tg)3 lymphocytes (2C) in an adop- http://www.jimmunol.org/ few that survive become memory cells that persist for a long pe- tive transfer model. The 2C TCR recognizes the Ld MHC class I riod of time, sometimes throughout the life of an animal (5–7). Ag and can be tagged by a clonotypic Ab (1B2) that permits the Memory T cells are specific to the Ag they encountered during the detection of small numbers of Ag-specific cells in vivo (20). We primary immune response and react rapidly upon re-encounter demonstrate here that CD8ϩ memory T cells can be efficiently with the same Ag. generated and maintained in the absence of IL-2. However, IL-2 The mechanisms responsible for the persistence of T cell mem- increased the size of the CD8ϩ memory population if present dur- ory are unclear. It appears that memory T cell populations are ing T cell activation but reduced its size if present during the main- maintained through the homeostatic replication of a subgroup of tenance period. These findings indicate that IL-2 has a dual role in ϩ memory cells and through the intrinsic ability of some memory the generation and maintenance of CD8 T cell memory. by guest on September 30, 2021 cells to survive in the resting state for an extended duration (8, 9). Although earlier studies suggested that continued antigenic stim- Materials and Methods ulation is required for maintaining T cell memory (9–12), recent Mice ϩ ϩ evidence indicates that CD4 and CD8 memory T cell popula- Ϫ Ϫ Ϫ Ϫ BALB/c (H-2d), C57BL/6 (H-2b) Rag1 / , and C57BL/6 IL-2 / mice tions persist in the absence of specific or cross-reactive Ags pre- were purchased from The Jackson Laboratory (Bar Harbor, ME). C57BL/6 sented by MHC molecules (13–15). Therefore, it is possible that 2C TCR-tg mice were provided by Dr. Dennis Loh and bred at the Veterans Ag-independent factors, such as cytokines, are critical for the sur- Affairs Medical Center animal facility (Atlanta, GA) (20). IL-2-deficient Ϫ/Ϫ vival and proliferation of memory T cells. IL-2 enhances the sur- 2C mice were generated by cross-breeding C57BL/6 IL-2 mice with C57BL/6 2C mice. Genotyping was performed by PCR amplification of vival of naive T cells and stimulates the proliferation of primary DNA extracted from tail clippings. Transgenic and gene-knockout mice activated lymphocytes (16, 17). In addition, it has been proposed were housed under specific pathogen-free conditions. that IL-2 is required for generating and maintaining memory T ϩ cells (18, 19). This hypothesis, however, is challenged by the find- In vitro generation of effector CD8 T cells ings that IL-2 programs T cells for activation-induced apoptosis Splenocytes were isolated from IL-2ϩ/ϩ and IL-2Ϫ/Ϫ 2C mice and stimu- and that IL-2Ϫ/Ϫ mice are not immunodeficient but instead display lated in vitro with mitomycin C-treated BALB/c splenocytes in RPMI 1640 exaggerated T cell immunity (4, 17). medium supplemented with 1 mM L-glutamine, 1% sodium pyruvate, 50 ␮M 2-ME, 100 U/ml penicillin, 100 ␮g/ml streptomycin (all from Life Technologies, Grand Island, NY), and 10% FCS (Sigma, St. Louis, MO). A total of 50 U/ml recombinant mouse IL-2 (Genzyme, Cambridge, MA) The Carlos and Marguerite Mason Transplantation Research Center, Renal Division, was added to all cultures. After 96 h of mixed lymphocyte culture, live Department of Medicine, Emory University and Veterans Affairs Medical Center, cells were isolated by ficoll density centrifugation using Lympholyte-M Atlanta, GA 30033 (Cedarlane, Hornby, Ontario) and were subsequently enriched for T cells by nonadherence to nylon wool columns (Polysciences, Warrington, PA). Received for publication April 17, 2000. Accepted for publication June 28, 2000. IL-2ϩ/ϩ and IL-2Ϫ/Ϫ 2C T cell-enriched preparations (a total of ϳ2.5 ϫ The costs of publication of this article were defrayed in part by the payment of page 107 2C T cells in each) containing 5 ϫ 106 CD8ϩ1B2ϩ cells (quantitated charges. This article must therefore be hereby marked advertisement in accordance by two-color flow cytometry as described below) were mixed with 3-fold with 18 U.S.C. Section 1734 solely to indicate this fact. more (ϳ7.5 ϫ 107) naive T cell-enriched IL-2ϩ/ϩ and IL-2Ϫ/Ϫ non- 1 This work was supported by National Institutes of Health Grants AI41643 (to TCR-tg C57BL/6 splenocytes, respectively, and were then adoptively F.G.L.) and AI44644 (to F.G.L.), and the Carlos and Marguerite Mason Trust for transferred by i.v. injection into Rag1Ϫ/Ϫ mice. Control Rag1Ϫ/Ϫ mice Transplantation (to F.G.L.). were adoptively transferred with 5 ϫ 106 naive IL-2ϩ/ϩ or IL-2Ϫ/Ϫ 2 Address correspondence and reprint requests to Dr. Fadi G. Lakkis, Veterans Affairs Medical Center and Emory University, Research 151N, 1670 Clairmont Road, At- lanta, GA 30033. E-mail address: [email protected] 3 Abbreviations used in this paper: tg, transgenic; BrdU, 5-bromo-2-deoxyuridine. Copyright © 2000 by The American Association of Immunologists 0022-1767/00/$02.00 3032 THE ROLE OF IL-2 IN CD8ϩ T CELL MEMORY CD8ϩ1B2ϩ cells mixed with ϳ7.5 ϫ 107 naive T cell-enriched IL-2ϩ/ϩ or 5-Bromo-2-deoxyuridine (BrdU) labeling Ϫ/Ϫ IL-2 non-TCR-tg C57BL/6 splenocytes, respectively. 2C lymphocytes ϩ/ϩ Ϫ/Ϫ were mixed with non-TCR-tg, syngeneic splenocytes before transfer to Naive IL-2 or IL-2 2C T cell-enriched splenocyte preparations that contain 5 ϫ 106 CD8ϩ1B2ϩ cells were mixed with ϳ7.5 ϫ 107 naive T simulate physiologic settings in which Ag-specific cells are present at ϩ/ϩ Ϫ/Ϫ much lower frequency than in TCR-tg mice. Mice were sacrificed at either cell-enriched IL-2 or IL-2 non-TCR-tg splenocytes, respectively, and were subsequently adoptively transferred to Rag1Ϫ/Ϫ mice by i.v. in- 1 wk or 10 wk after adoptive transfer and spleen and lymph node cells Ϫ/Ϫ were harvested to test for the presence of CD8ϩ1B2ϩ cells. Memory jection. Twenty-four hours later, the Rag1 hosts were immunized i.p. cells were identified according to the following criteria: 1) survival ad- with mitomycin C-treated BALB/c splenocytes. At 10 wk, 0.8 mg/ml BrdU vantage over naive cells; 2) high CD44 and low CD62L expression was added to the drinking water for 7 days, after which the mice were high low sacrificed and lymph node cells were harvested.